Your game is written in C, but the SNES does not eat PNGs, Tiled maps, or WAV files — it eats tiles, tilemaps, BGR555 palettes, BRR samples, and SPC700 soundbanks. The OpenSNES tools are the converters that bridge the two: each takes an artist- or musician-friendly source format and emits the exact binary the hardware (and this SDK's runtime) expects.

You rarely run most of them by hand — the build system wires the common ones in, so dropping a .png or .wav in an example's res/ is usually enough. But knowing what each tool does, and which knobs it exposes, is what takes you from "the example builds" to "I shaped my own assets on purpose." That confidence is what this section is here to give.

The pipeline

Most assets flow through a short, one-way pipeline from source art to ROM data:

RGB art ──► img2snes ──► gfx4snes ──► tmx2snes ──► map engine
 (.png)     (quantize)   (tiles +     (Tiled map     (mapLoad)
                          palette +     + that .map
                          tilemap)      → map binaries)
 
font.png ──► font2snes ──► text tiles      (dmaCopyVram)
sound.wav ─► wav2brr   ──► .brr sample     (audioLoadSample)
music.it ──► smconv    ──► SNESMOD bank    (spcLoad / spcPlay)

Each tool does exactly one conversion; the Makefile chains them. It is the Unix-pipe idea applied to asset building — small, composable, individually testable steps rather than one opaque converter.

The tools at a glance

Tool	Turns…	…into	In your build
gfx4snes — images to tiles, palettes & maps	an indexed PNG/BMP	tiles + palette + tilemap	auto (drop a PNG in GFXSRC)
tmx2snes — Tiled levels to SNES map data	a Tiled JSON map	tilemap + collision + objects	one line per example
img2snes — RGB artwork to indexed palettes	RGB/RGBA artwork	a palette-indexed PNG (feeds gfx4snes)	manual pre-step
font2snes — font images to text tiles	a 96-glyph font PNG	2bpp/4bpp text tiles	manual, optional
wav2brr — WAV to BRR sound samples	a PCM .wav	a .brr sound sample	auto (drop a WAV in res/)
smconv — tracker modules to SNESMOD soundbanks	an Impulse Tracker .it	a SNESMOD soundbank	auto (USE_SNESMOD)

Three levels of wiring

The tools sit at three levels of automation — worth knowing so you reach for the right one:

Zero-config, automatic. gfx4snes (via the GFXSRC Makefile variable) and wav2brr (any res/*.wav) and smconv (USE_SNESMOD := 1) run for you during make. Drop the source in, reference the output, done.
One explicit line. tmx2snes is called from an example's own Makefile, because a Tiled project has choices (which layers, which extra outputs) the build cannot guess.
By hand, when you need them. img2snes (RGB → indexed) and font2snes (custom font) are standalone pre-steps you run once and commit the result. Looping wav2brr samples are also hand-built (the loop points are yours).

All binaries live in bin/ and are built by make tools. Every tool prints --help; the pages here are the guided version.

Where they fit with the rest of the docs

The why behind the numbers these tools produce — bpp, VRAM cost, palette conventions — is Planning your SNES game. Read it before you commit to a mode.
The level workflow that gfx4snes + tmx2snes enable end-to-end is From tiles to levels and the Scrolling maps tutorial.
The audio side pairs with SNES Sound Programming Guide and Audio & Music Tutorial.

The one rule. Keep the source (the PNG, the Tiled project, the WAV, the .it) as your single source of truth and let the tools regenerate the binary on every build. The moment you hand-edit a .pic or a .brr, it drifts from its source and you have lost the pipeline's whole benefit.